1. Jeannin
Basically there were three main types of aircraft built by Emile Jeannin, of which a number of subvariants appeared:
• the 1911 Eindecker
• the 1912 Taube
• the 1913 Stahltaube
I have my doubts concerning the so-called Jeannin biplane (Gray/Thetford, p. 429). It is not of Jeannin style (a biplane with swept wings), and apparently it was designed by Karl Bomhard, who worked for Union and built there a number of other swept winged airplanes.
In 1915 the Emile Jeannin Flugzeugbau GmbH was taken over by National-Flugzeugwerke GmbH (itself created earlier by DFW as a subcontractor).
Emile Jeannin was an Alsatian by origin, born in the then German Mühlhausen i. Elsaß (now the Franch Mulhouse). He had always been a colourful character. He was a very good aviator, but also a star. At the beginning of WWI he got a severe sentence for an affair with a minor girl. But he wasn't the only one in Germany at that time. Ellery von Gorissen also had a lot of trouble for an affair with a minor boy… But let us focus on airplanes
2. Naglo
Concerning an eventual Naglo training biplane I have no information. Interesting. Where did you find the information?
3. LVG D4
D4 was the company designation of the LVG B.I